Effects of fatty acid composition on the sensitivity of membrane functions to ethanol in Escherichia coli.

The effects of membrane composition on the sensitivity of membrane functions to ethanol in Escherichia coli have been investigated. The addition of ethanol (0.67M) in vitro did not cause appreciable inhibition of NADH oxidase, D-lactate oxidase or ATPase but caused an 11% to 30% inhibition of succinic dehydrogenase, glutamate uptake, proline uptake and 1ac permease. Although the sensitivities of some of these membrane functions to ethanol varied with membrane composition, none correlated with the changes in sensitivity to killing by ethanol. In contrast, leucine transport was resistant to ethanol (0.67M) in control cells and in cells enriched in vaccenic acid, but was inhibited by 25% in cells grown in palmitic acid. The release of nucleotides was examined as a comparative measure of cellular permeability. Ethanol increased nucleotide leakage. Leakage was reduced in cells grown in vaccenic acid and enhanced in cells enriched in palmitic acid. The addition of MgSO4 (10mM) reduced nucleotide leakage and enhanced survival. Based upon these results, metabolite leakage was proposed as the primary event associated with bacterial inactivation in buffered solutions of ethanol. The increase in acyl chain length is proposed as the beneficial aspect of vaccenic acid incorporation rather than the increase in membrane unsaturation.